1. Field of the Invention:
The present invention relates to a method for adjusting an insertion amount of an adjusting pipe for a fuel injection valve.
2. Description of Related Art
A conventional method for adjusting an insertion amount of an adjusting pipe 15 will be described with reference to FIGS. 1 and 3.
A frequency, a pulse duration, a pulse amplitude of an electric current supplied into a coil 15 are fixed at predetermined amounts. An injection amount per valve stroke, of each sample fuel injection valve, in accordance with the predetermined electric current is different from each other. Since the frequency of the electric current is fixed, when the injection amount is defined, a flow amount per unit time in accordance with the electric current is also defined. In this prior art, the insertion amount of the adjusting pipe is adjusted by supplying the fixed electric current having a constant frequency, a constant pulse durability, and a constant pulse amplitude into the fuel injection valve 10, and inserting the adjusting pipe 15 a housing 11 to change the injection amount until the flow amount reaches a target flow amount.
A back pressure valve 24 regulates the pressure of fluid flowing into the fuel injection valve 10 from a pump 20. Next, a motor 30 rotates to insert the adjusting pipe 15 to a predetermined position where a spring 14 generates a spring force to urge a needle 12 to reach a valve seat 11a. 
A personal computer 40 receives a flow amount signal from a flow meter 23 and calculates the fluid flow amount per unit time. Since the insertion amount of the adjusting pipe 15 is small and the spring force of the spring 14 are small, the flow amount calculated by the personal computer 40 is larger than target flow amount.
An insertion amount is attained based on a relation map of the insertion amount and a difference between the calculated flow amount and the target flow amount. The relation map is previously memorized in a ROM of the personal computer 40. The relation map differs in accordance with the specificity of each 20 fuel injection valve.
The personal computer 40 controls a driving circuit 41 to supply an electric current based on the attained insertion amount into the motor 30. The motor 30 rotates to insert the adjusting pipe 15 into the housing 11 through an insertion screw 30.
The adjusting pipe 15 is inserted into the housing 11 to increase a valve opening period and decrease a valve closing period of the fuel injection valve 10, so that the injection amount is reduced, thereby reducing the fluid flow amount. Here, since a fluid flow becomes unstable due to the flow amount reduction, it is necessary to wait until the flow amount becomes stable to be constant to calculate a flow amount at this time based on a flow amount signal from the flow meter 23. When the calculated flow amount becomes within standard range from the target flow amount, the insertion amount adjusting procedure is finished. If the calculated flow amount is out of the standard range, the above described adjusting cycle is repeated until the calculated flow amount becomes within standard range from the target flow amount.
However, according to the above described conventional adjusting procedure, since the flow amount is reduced due to the insertion of the adjusting pipe 15, it is necessary to wait until the flow amount becomes stable to be constant to calculate a flow amount at the time when the insertion of the adjusting pipe 15 is completed, thereby increasing a total adjusting time.
Further, since the adjusting pipe 15 is press inserted into the housing 11, the adjusting pipe 15 cannot return to the previous position thereof when the adjusting pipe 15 is excessively inserted into the housing 11. Thus, the one cycle insertion amount based on the relation map is determined smaller than an insertion amount attaining the target flow amount, for preventing the adjusting pipe 15 from inserting excessively. Thus, it is difficult to adjust the insertion amount accurately with respect to an optimum insertion amount that can attain the target flow amount. As a result, even final flow amount attained by repeat of the insertion amount adjusting procedure must be larger than the target flow amount although it is within the standard range from the target flow amount, so that it is difficult to attain the target flow amount accurately.
An object of the present invention is to reduce a time for adjusting an insertion amount of an adjusting pipe, and to adjust the insertion amount accurately.
According to a first aspect of the present invention, an adjusting pipe is being inserted while changing an electric current for a coil to keep a flow amount of a fluid at a predetermined flow amount constantly. When the electric current supplied into the coil becomes a target electric current, the adjusting pipe is stopped being inserted, and the electric current is stopped being changed. That is, since the insertion amount of the adjusting pipe and the electric current are continuously adjusted and changed while keeping the flow amount constantly, there is no need to wait until the flow amount becomes stable as in the conventional adjusting method in which a fluid flow amount is decreased toward a target flow amount. Thus, the adjusting time is reduced.
Further, since the insertion amount of the adjusting pipe is adjusted while keeping the flow amount at the target flow amount, the insertion amount is accurately adjusted. Thus, the flow amount and an injection amount are highly accurately adjusted within the standard range from the target flow amount.
The adjusting method of the first aspect of the present invention is attained by merely changing a control program of a conventional adjusting system, so that there is no need to prepare an additional adjusting system.
According to a second aspect of the present invention, the electric current is changed by adjusting a frequency or a pulse duration thereof. An adjustment of the frequency or the pulse duration is easily done by a microprocessor or the like.